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Full text of "The manufacture and properties of iron and steel"

OLASSIPICATIOl^   OP  STRTTOTUEAL  STEELS.
39?
that the elastic ratio -rises as the ultimate strength, decreases is not generally recognized, but will be shown in Table XVIII-A. This compares the groups of angles in Table XIV-H, which are made by the same process, and are of the same thickness, and contain the same percentage of phosphorus. In every case the stronger steel gives a lower elastic ratio.
TABLE XVIII-A.
Else in Elastic Ratio with Decrease in Ultimate Strength.
									o
	43	03	Harder steels.			Softer steels.			*H
	s	bO S							as
				O M	o		O in	o	
	Sft				a		S'S	S	.- 0)
03	&	0   .	-2. .S'o	as	m c3 M	4"* ..,03 O	gg	m c3 M	4=43 tfl &Q
S m * 1	1! 0 a -3 gft	sJ 3 ^ 2-2	fff|	. X	verage el ratio; pe cent.	3 ttDn3 33 f> tn P<oi		verage el ratio; pe cent.	ise in ela in softer per cent.
M	0	H	<J	!	<	q	<l	4	K
		A to f	68865	89692	67.43	52588	86284	69.07	1.64
Basic o. H.	below .04	A Jo! A to I	68588 69235	87827 87487	64.62 68.28	58171 51903	84891 84026	65.62 65.56	1.00 2.28
		it to I	59125	86035	60.95	61923	82856	62.81	1.86
Acid O. H.	.05 to .07	A to 1	65656 65681	48718 42191	66.58 64.28	60845 60695	40891 89415	67.21 64.94	0,68 0.66
Acid O. H.	.07 to .10	A tof A to 2	66865 65777	44486 42817	67.03 65.09	60064 60583	41148 40170	68.50 66.80	1.47 1.21
Aoid Bess.	.07 to .10	A .Jo f A to j	66277 65940	46422 45280	70.04 68.66	60659 59882	43417 42518	71.58 ,71.00	1.54 2.84
The tendency in the first epoch of steel structures was toward a hard alloy, but later practice has been a continual progress toward toughness. There was a halt at a tensile strength of 60,000 pounds, not on account of any magic virtue in the figure, but because ordinary mild steels gave that result, and a higher price was charged for softer metal. Conditions today are different, for the introduction of the basic hearth has altered the economic situation. A steel of 50,000 to 58,000 pounds per square inch is a most attractive material, possessing all the good characteristics of wrought-iron with greater strength and toughness.
In many specifications the option is given between acid and basic open-hearth steel, but1 it costs more to make low-phosphorus metal by the acid than by the basic process, so that the terms of the specification should be enforced after the contract is awarded, out of justice to other bidders who have based their calculations on the